Passive devices such as an inductor, a capacitor, and a resistor are integrated on a silicon substrate, a glass substrate, or a ceramic substrate to form a passive device substrate that is known in the art as an integrated passive device. An integrated passive device typically has an inductor having an air core, and the passive devices such as an inductor, a capacitor, and a resistor fabricated in an integrated passive device tend to have small impedance values. These devices are used in a circuit that passes high-frequency signals (i.e., high-speed signals).
An integrated passive device may be formed as a laminated structure with other devices such as another integrated circuit, or may be flip-chip mounted on a wiring substrate. In such a case, an inductor of the integrated passive device that has an air core structure may be affected by the other devices and the interconnection patterns of the wiring substrate. Because of this, the inductance value and Q value of the inductor may deviate from designed values.
Further, a high-frequency signal (i.e., high-speed signal) flowing in an integrated passive device may function as a noise source that affects other devices and the interconnections of a wiring substrate. Implementation utilizing an integrated passive device structure thus requires placement and mounting that take into account the characteristics of an integrated passive device, and also requires restriction on the design of a wiring substrate.
As described above, the related-art integrated passive device structure gives rise to a difficulty in providing desired circuit characteristics for implemented passive devices, and also serves as a noise source.
Accordingly, it may be desirable to provide a passive device substrate that enables the provision of desired circuit characteristics for implemented passive devices and also enables the reduction of noise.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2010-109351